42 . H. C. RUSSELL. 
to be of great purity, and that it will bear favourable comparison 
with the water supplied to the chief cities in the world. 
The Board of Water Supply and Sewerage have in Sydney 
introduced a system of ventilating which has been developed by 
Mr. J. M. Smail, Engineer for Sewerage. It is, I understand an 
improvement upon any system of ventilating sewers in actual _ 
operation, in fact at this moment the sewers of Sydney are in a 
better sanitary condition than those of any other city in the world. 
And it seems fitting that in an attempt to get together a record 
of the applications of science, as well as pure science, that I should - 
say a few words about a subject of such vital importance to the 
health of the city. The members are doubtless all familiar with 
Banner’s system of ventilating sewers which was developed in 
Brighton, England, by Mr. Banner, as an attempt to get rid of 
sewer gases from his own house, and since 1873 has spread to so 
many cities ; in fact, no city with any pretentions to sanitary care 
is without some form of it. The principle is that the atmosphere 
should have free ingress to and egress from sewers at the crown 
of the roads, so that by oxidation it to a great extent destroys 
the noxious gases, and at the same time prevents the accumulation 
of sewer gas under pressure, and hence stops it from forcing its 
way into houses through the drainage pipes and traps. Before 
attempting to apply this system to Sydney, Mr. Smail determined 
to see if the upcast and downcast circulation of air and gas would 
go on as satisfactorily in a hot climate as it did in a cold one, and 
he found that it did not, and that when any wind was blowing, 
it became the principal factor in producing a circulation of air 
in the sewers. If the wind blew towards the outfall of any sewer, 
the air was forced up the manholes into the roadway, and although 
much diluted in the process, it was sufficiently noxious to cause a 
nuisance, especially in narrow streets, in densely populated areas; 
guided by these investigations the system he adopted is to close 
these openings in the street, and supply the sewers with fresh air 
by downcast pipes, and at the same time provide an upcast pipe 
for exhausting the air and gas from the sewer, the first stage of 
